Peel the russet potato and cut into 1-inch cubes, then place in a pot of salted water and boil for 12-15 minutes until fork-tender.
While potatoes boil, season the chicken breast with olive oil, half of the sea salt, and half of the black pepper.
Heat a skillet over medium-high heat and sear the chicken for 5-7 minutes per side until the internal temperature reaches 165°F, then let it rest.
Finely mince the garlic cloves and gently sauté them in a small pan with the ghee for 1-2 minutes until fragrant but not browned.
Drain the cooked potatoes and return them to the pot, mashing them thoroughly while they are still hot.
Fold in the plain Greek yogurt, sautéed garlic with ghee, remaining sea salt, and black pepper until the texture is smooth and creamy.
Finely chop the fresh chives and stir them into the mashed potatoes just before serving.
Slice the rested chicken and serve it alongside the buttery garlic mashed potatoes for a complete, high-protein meal.